Blood is in liquid form when traveling undisturbed in bodily passageways. However, an injury may cause rapid clotting of the blood at the site of the injury to initially stop the bleeding, and thereafter, to help in the healing process. An accurate measurement of the ability of a patient's blood to coagulate in a timely and effective fashion and subsequently to lyse is crucial to certain surgical and medical procedures. Also, accurate detection of abnormal hemostasis is of particular importance with respect to appropriate treatment to be given to patients suffering from clotting disorders.
Blood hemostasis is a result of highly complex biochemical processes that transform the blood from a liquid state to a gel state. Characteristics of blood, such as strength of the clot and other mechanical properties of the blood are useful in determining its hemostasis characteristics. For example, if the strength of the clot can resist the shear forces of the circulating blood, that clot can adhere to a damaged vascular site (e.g. open vascular system following surgery) and stop bleeding. That same formed clot in an undamaged (i.e. closed) vascular system will impede the flow of blood and, depending on its location, can cause heart attack, ischemic stroke, pulmonary embolism (PE), or deep vein thrombosis (DVT).
In accordance with commonly owned U.S. Pat. No. 8,236,568 entitled Method of Analyzing Hemostasis; U.S. Pat. No. 7,879,615 entitled Hemostasis Analyzer and Method and U.S. Pat. No. 7,261,861 entitled Hemostasis Analyzer and Method, the disclosures of which are hereby expressly incorporated by reference, a description is provided of apparatus and methods for hemostasis analysis by observation of sample resonant response to dynamic excitation. A blood hemostasis analyzer in accordance with the teachings of these patent operates under the principle that because hemostasis of a blood sample changes the blood sample from a liquid state to a gel state, and the viscoelastic properties of the clot formed by coagulation controls the natural frequency of the sample, measuring changes in the natural frequency of the blood sample during coagulation provides the hemostasis characteristics of the blood sample. In keeping with this principle, the blood hemostasis analyzer measures the changes in the natural frequency of a blood sample during coagulation and lysis to provide hemostasis characteristics of the blood sample. To measure hemostasis in this manner, the analyzer generally includes a container for holding the blood sample, a shaker or exciter for displacing the container to excite the blood sample to resonant vibration, and a sensor for measuring the resulting amplitude of motion of the blood sample.
The above-patented method of hemostasis analysis provides for vibration of a sample to resonance. As blood transitions from a liquid state to a gel state, such as a substantially dilute cross-linked system, exhibiting no flow at steady-state, the natural frequency of the blood sample increases. Hence, measuring the changes in the natural frequency of the sample under excitation and during clotting and lysis provides a hemostasis indication.